Device for producing rapidly flying ions



Oct. 7, 1941. w. scHUTzE 2,258,149

DEVICE FOR PRODUCING RAPIDLY FLYING IONS Filed April 22, 1939 123 F/Z a'NON-MAGNETIC 9 man/[77c P016 PIECE POLE PIECE merited Oct. 7, 1941Werner Schiitae, Berlin-Pankow,.

signer to Fides-Gesellschait liir Germany, al-

die Verwaltnng 11nd Verwertnng yon gewerblichen Schntarechten mitbeschrankter Battling, Berlin, Germany, acorporationof Germany 7Application April 22, 1939, Serial No. 269,452

8 Claims.

This invention relates to adischarge device for producing ions of highvelocity.

In a known arrangement of this type, the ions are produced in agas-filled discharge chamber whence they pass at a given velocitythrough a relatively narrow aperture into a vacuum chamber in which theyare further accelerated. When using such iontubes it has been found thatthe production of highly accelerated ions-in proportion to the input ofthe tube, 1. e.- the efliciency,

is lower than expected, and that the anode struc- Germany April 23, 1938aperture 2 of both chambers. A cathode of such design isdescribed in theapplication of Curt Hailer, Serial No. 222,607, filed August 2, 1938.

It has been found that the ions produced in the anode chamber arealready accelerated within the anode to relatively high velocities andfly in the direction towards the aperture 2. When flying, the ions oftenrecombine with the electure of the tube is liable to be overheated,particularly in local areas.

, The main object of the present invention is to eliminate or greatlyreduce these drawbacks. To this end, in a discharge device for theproduction of rapidly flying ions having an ion source consisting of agas-filled discharge chamber as-' sociated with an evacuatedacceleration chamber, a magnetic field is caused to act upon the ions inthe neighborhood of the cathode aperture and to prevent the electronsreleased at the cathode from reaching the anode aperture opening.

The invention will be understood from the following description of thedevices shown in the drawing in which Fig. 1 represents a? longitudinalsection through the electrode arrangement of a discharge deviceaccording to the present invention, the magnetic energization and hencethe ,above-mentioned magnetic field being not in operation.

Fig. 2 shows substantially the same arrangement, the magnetic fieldbeing operative.

Fig. 3 shows diagrammatically a part-sectional side elevation of acomplete discharge device employing an electrode arrangement similar tothose of Figs. 1 and 2.

Fig. 4 is a diagrammatic illustration of electric magnetic means forproducing the magnetic field above referred to, and

Fig. 5 shows a top view of the cathode structure of the arrangementshown in Fig. 2.

In Fig. 1, i denotes a gas-filled discharge chamber in which the ionsare produced, 2 is a narrow aperture forming an outlet for the ionsproduced in chamber I, 3 is the highly evacuated vessel portion in whichthe ions are accelerated to very high velocities before passing throughthe aperture 6 of the cathode 4 and before bein trons present inside theanode chamber to form neutral gas particles which, however, continue tofly approximately at the velocity of the accelerated ion. Most of theseneutral gas particles pass through the aperture 2 into the vacuumchamber and fly in the latter in the direction of the cathode.. Theneutral gas particles fly in different directions owing to theprevailing speed distribution, and afocussing oi the neutral particlesdoes not take place so that a large number of them impinge .with'greatforce upon the surface of the cathode 4, where secondary electrons arereleased which are considerably accelerated in the direction towards theanode. At the same time the stream of electronstowards the anode isfocussed, and the secondary electrons released at the surface portions Iand 8 of the cathode reach the aperture 2 in the form of a dense stream,part of which passes through its aperture into the anode chamber I. Thisinverse electron current represents a loss. Besides, a large portion ofthe stream of electrons impinges upon a very small surface of the anode,thus heating it locally to a considerable temperature.

Fig. 2 shows the conditions which prevail in the same electrodearrangement if a magnetic field is produced in the neighborhood of thecathode. The cathode 4 is composed of two magnetic pole pieces l3 and IH which produce a steady magnetic field represented by the lines offorce IS. The intermediate sections 9 and H of the cathode (Fig. 5)consist of non-magnetic metal. If now secondary electrons are releasedin the above-described manner at the surface of the cathode 4, they aremagnetically influenced in the very neighborhood of the cathode wherethey have not yet attained a high speed and thus are scattered fromtheir original direction of flight into different directions dependingupon the initial direction and speed of the electrons. The electronsemitted from the cathode surface,

therefore, either fly back to the cathode or they reach the anode alongmore or less spiral-shaped paths (as indicated by the arrowed lines l6,l1 and I8) without being able to form a dense stream of electrons due tothe iocussing action of the electric lens. The points of the anode 5upon which the electrons impinge are therefore disstream of ions I!however, remains practically .unbiased, since the ions have already avery great speed when entering the effective range of the magnetic fieldand since the field exerts a slighter efiect on the ion current than onthe electron current.

The magnetic'fleld about the cathode may be produced in any suitablemanner. Thus, for instance, two pole pieces l3 and I may be magnetizedby an electric energizing coil or-by a permanent magnet. The two polepieces, for instance, may be connected with each other by a suitableyoke and form with the latter a permanent magnet. The pole pieces mayalso be arranged in a difierent manner, for instance slightly above thecathode surface facing the anode, the only essential requirement beingthat the mag netic field be eifective in the immediate neighborhood ofthis surface.

The importance of the invention will be readily apparent if it isconsidered that in the known arrangements the neutral gas particles mayassume a very high velocity, for instance of-50 kv., suflicient torelease a current of electrons at the cathode greater than the currentof ions produced. The force with which this electron current impingesupon the anode is so great as to produce intensive X-rays. In the caseof an electron current of only 1 ma., a magnitude which may easily bereached or surpassed, and an anode voltage of 1000 kv., every 7 mm. ofsurface have to carry a wattage of 1 kw. if the diameter of the streamof electrons amounts to 3 mm. This wattage is converted into heat uponthe impinging of the electrons. However, by employing' a magnetic fieldthis waste heat and its distributing eifects are virtuallyeliminatedaccording to the invention.

Fig. 3 exemplifies the construction of a complete arrangement accordingto the invention.

The discharge vessel has a porcelain'wall 2|, in

which is arranged the anode structure 30, whereas the cathode 23 issecured to the bottom 24 of the vessel. The cathode 23 is designed inthe manner shown in Figs. 1 and 2. It consists of the two magnetic polepieces 25 and 26 magnetically connected with each other by a yoke 2! andenergized by coils 28 and 29, as shown in Fig. 4. The ions produced inthe gas chamber 22 of the anode fly through the anode aperture 'andthrough the aperture of the cathode 23 into the chamber 3| in which thematerial 33 to be treated is placed on the bottom of a Faraday cage 32.The acceleration voltage for the ions is applied between the terminals34 and 35. The portion of the chamber of the vessel to be evacuated-i.e. the entire vessel chamber with the exception of the gas-filled ionproducing chamber 30-is evacuated by a high-vacuum pump connected to thesuction conduit 36. The intensity of the ion current may be measured bymeans of an ammeter 31.

What is claimed is:

1. A discharge device for producing ions of high velocity, comprising avacuum chamber, an anode having a gas-filled chamber forming the sourceof the ions and provided with an aperture for the passage of the ionsinto said vacuum chamber, a cathode in said vacuum chamber foraccelerating the ions, and non-focussing magnetic means associated withsaid cathode for producing a dispersing magnetic field effective at thesurface of said cathode so as to prevent electrons released at saidcathode from forming a directed beam impinging on said anode.

2. A discharge device for producing ions of high velocity, comprising avacuum chamber, an

anode having a gas-filled chamber forming the source of the ions andprovided with an aperture for the passage of the ions into said vacuumchamber, a cathode'in said vacuum chamber for accelerating the-ions,said cathode comprising ferromagnetic pole pieces for producing adispersing magnetic field effective at the surface of said cathode so asto prevent electrons released at said cathode from forming a direc beamimpinging on said anode.

3. A discharge device for producing ions of high velocity, comprising avacuum chamber, an anode having a gas-filled chamber forming the sourceof the ions and provided with an aperture for the passage of the ionsinto said vacuum chamber, a cathode in said vacuum chamber foraccelerating the ions, said cathode having a central aperture for thepassage of the ions, and comprising two ferromagnetic pole piecesbordering said cathode aperture and arranged diametrically opposite eachother, and means for energizing said pole pieces to produce a dispersingmagnetic field eflective at the surface of said cathode so as to.unfocuselectrons released at said cathode to prevent them from forming adirected beam impinging on said anode.

4. A discharge device for producing ions of high velocity, comprising avacuum chamber, an anode having a gas-filled chamber forming the sourceof the ions and provided with an aperture for the passage of the ionsinto said vacuum chamber, a cathode in said vacuum chamber foraccelerating the ions, said cathode having a central aperture for thepassage of the ions, and comprising two ferromagnetic pole piecesbordering said cathode aperture and arranged diametrically opposite eachother, a ferromagnetic yoke connecting said pole pieces with each other,and an electric energizing coil disposed on said yoke for magnetizingsaid pole pieces.

5. A discharge device for producing ions of high velocity, comprising avacuum chamber, an anode having a gas-filled chamber forming the sourceof the ions and provided with an aperture for the passage of the ionsinto said vacuum comprising two ferromagnetic pole pieces bordering saidcathode aperture and arranged diametrically opposite 'each other, apermanent magnet structure including said pole pieces for producing amagnetic field effective at the surface of said cathode so as to unfocuselectrons released at said cathode to prevent them from forming adirected beam impinging on said anode.

6. A discharge device for producing ions of high velocity, comprising avacuum chamber, an anode having a gas-filled chamber forming the sourceof the ions and provided with an aperture for the passage of the ions,into said vacuum chamber, a cathode in said .vacuum chamber foraccelerating the ions, said cathode having a central aperture for thepassage of the ions, and comprising two ferromagnetic pole piecesbordering said cathode aperture and ar ranged opposite each other,intermediate pieces of non-magnetic metal also bordering said apertureand connecting said pole pieces with each other, and means forenergizing said pole-pieces so as to assume opposite magnetic polaritiesto produce a magnetic field for diverting electrons released at saidcathode to prevent them from forming a directed beam impinging upon saidanode.

'7. A discharge device for producing ions of high velocity, comprising avacuum chamber, an anode having a gas-filled chamber forming the sourceof the ions and provided with an aperture for the passage of the ionsinto said vacuum chamber, a cathode in said vacuum chamber foraccelerating the ions, said cathode comprising ferromagnetic elements ofdifferent magnetic polarity so as to produce a dispersing magnetic fieldfor preventing electrons released at said cathode from reaching saidanode as a directed beam.

8. A discharge device for producing ions of high velocity, comprising avacuum chamber, an anode having a gas-filled chamber forming the sourceof the ions and provided with an aperture for the passage of the ionsinto said vacuum chamber, a cathode'in said vacuum chamber foraccelerating the ions, and non-focussing magnetic means for producing atthe surface of said cathode a dispersing magnetic field whose lines offorce extend substantially perpendicularly to the direction of moz ementof the ions flying through said aperture towards said cathode.

\ WERNER

